1. Field of the Invention
The present invention relates to an inductive heating roller apparatus.
2. Description of the Related Art
As commonly known, the inductive heating roller apparatus is structured by arranging an inductive heat generation mechanism provided with an inductive coil inside a rotating roller. In such the structure, when the inductive coil is excited by the AC power source, the magnetic flux is generated along the shaft center direction of the roller, and the magnetic flux passes through a closed magnetic path one portion of which is formed of the peripheral wall of the roller, and by this magnetic flux, the current is induced in the roller, and the peripheral wall of the roller is heat-generated by the Joule heat due to this current.
As being understood by this description, because the closed magnetic path for the generated magnetic flux is a single closed magnetic path including the peripheral wall of the roller, the AC power source to excite the inductive coil is limited to a single phase power source. On the one hand, in general factories, because three-phase power source is a main power source, it is required that the inductive coil is excited by the three-phase power source.
However, in order to obtain the single phase voltage from the three-phase power source, when two lines of the three-phase lines are used, and the single phase voltage is obtained from between the two lines, and this voltage is applied onto each inductive coil, the unbalance of the power source is generated between the case of two lines between which the inductive coil is connected, and the case of two lines between which the inductive coil is not connected. Accordingly, the utilization efficiency of the power source is lowered.
The object of the present invention is to apply the single phase voltage onto the roller without generating any unbalance in the three-phase power source, when the three-phase power source is used as the power source for the roller heat generation.
In the structure of the present invention, an inductive heat generation mechanism having an inductive coil is arranged inside a rotating roller, an inverter having a three-phase power source as an input power source, and outputting the single phase voltage by the phase conversion is prepared, and the single phase output voltage from the inverter is applied onto the inductive coil as the exciting voltage.
As an inverter, an inverter using, for example, a SCR, or a transistor can be appropriately used. Also in any one of inverters, in order to obtain the single phase voltage from the three-phase voltage, the three-phase voltage is converted once into the DC voltage, and the DC voltage is converted again and the single phase voltage is obtained. In such the manner, when the single phase voltage obtained from the three-phase voltage is used for the excitation of the inductive coil, no unbalance is generated in the three-phase power source which is the input power source.
When a plurality of inductive coils constituting the inductive heat generation mechanism are provided, the single phase voltage obtained from the inverter may also be applied on each of inductive coils as the exciting voltage. In this case, when the single phase voltage applied onto each of inductive coils is the same phase to each other, the closed magnetic path for the magnetic flux induced by each of inductive coils, is independent of each other, and the interference does not occur with each other.
A value of the single phase output voltage of the inverter can be adjusted by changing an arc angle of SCR constituting the inverter. Accordingly, in the case where a plurality of inverters are prepared, and respective single phase output voltage are applied onto respective inductive coils, when each of inverters is independently adjusted, an amount of the magnetic flux induced by each of inductive coils can be adjusted, and accordingly, the peripheral wall temperature of the roller can be freely changed along the length direction of the roller.